That might be true except cars have vastly different wheel sizes and wheelbases. One video would only work for a single platform. Even then, the company states that the rig is customized per car to get the ride height and tire size right.

I think they use CG cars instead of real ones for the same reason everything is CG: cost. It's cheaper to just rent one of these from a local film studio than sending out a small fleet of actual cars to film in whatever salt flat they are using this time. It also gives them more control of the look and design of the car. Did you know that 75% of the items in an IKEA catalog are CGI?

Also, I wouldn't be surprised (given the tight release schedule of some car models and the secrecy around them) that this lets them film the advertising of a car concurrently with the final production stages. They don't have any cars coming off of the line to shoot with, so it's easier to rig up the wheelbase (which is established early in production) and get the marketing done concurrently.